man -k xyz will search for any man page with xyz in it. You can also do man stdio to see what's in the stdio library.

I wrote a little script to browse Manpages: woman using fzf to create such a browser. Just run woman without arguments to see the full list.

I think you would need to change the variable sections='1,8,6,5,7' , so it access only specific Manpages. In example 1 stands for executable programs or shell commands. More about the sections in the DESCRIPTION of the man command itself: man man

ls /usr/share/man/man?/* will show you all the man pages on your system. I used to pick ones at random.

Originally there were a number of manuals. Manual 1 had user commands. Manual 2 had system calls. Etc. You can type man NUMBER intro to read about that manual. You can also use man -k or appropos but I've also just used grep. These days they're compressed so zgrep.

On Archlinux at least, the glibc package includes info pages for C functions. Just type info libc at the command line, or use info inside emacs. There are hyperlinks in info pages, it's a nicer interface than man pages.

On Debian, there is a package that displays system documentation including, if I remember correctly, man pages. I think I had to set up a local web server first.